The present invention relates to apparatus for treating webs of photographic material or the like, particularly for severing a web of photographic paper in a processing laboratory at regular or irregular intervals to thereby subdivide the web into a series of discrete prints which are collected together with the corresponding film or films and shipped to or picked up by customers.
It is already known to transport a web which carries a series of images of film frames in an apparatus wherein the actuation of a suitable severing or cutting device is initiated in response to detection of indicia in the form of graphite marks, notches, perforations or the like applied to the web at such intervals that each indicium is located at a predetermined distance from a line along which the web is to be severed to separate therefrom the foremost print of a customer order.
A drawback of presently known apparatus is that the detector means which is used to scan the web for the presence of indicia and to produce signals serving to initiate successive severing operations is likely to produce such signals in response to detection of unintentionally applied or accidentally formed indicia. For example, a detector means which employs a photoelectric cell is likely to produce a signal in response to detection of a crack, a foreign particle, a tear in a marginal portion of the web and/or other imperfections whereby the web is likely to be severed across the image of a film frame or to be severed between a frame line and the adjacent image.
Another drawback of presently known apparatus is that their detector means is not capable of invariably detecting the indicia, particularly graphite marks which are normally applied to the rear side of a web of photographic paper, if the quality (particularly the sharpness) of indicia is affected by liquid when the web must be transported through one or more liquid baths prior to reaching the severing station. The detector means often responds to detection of localized contamination of a travelling web which is likely to occur when the web is caused to travel through a developing machine with one or more liquid baths and one or more drying stations. The situation is analogous when the indicia are in the form of marks which are exposed on the emulsion-coated front side of the web; such indicia are also likely to be confused by detector means with spots or particles of foreign matter on the travelling web.